(06-10-11) The Effects of a Higher Protein Intake During Energy Restriction on Changes in Body Composition and Physical Function in Older Women

Mojtahedi MC, Thorpe MP, Karampinos DC, Johnson CL, Layman DK, Georgiadis JG, Evans EM.
Source
Department of Sports Medicine, Institute of Sports Sciences, Justus Liebig University Giessen, Kugelberg 62, 35394 Giessen, Germany. [email protected].
Abstract
BACKGROUND:
The purpose of this double-blind randomized clinical trial was to compare the relative effectiveness of a higher protein and conventional carbohydrate intake during weight loss on body composition and physical function in older women.
METHODS:
Thirty-one overweight or obese, postmenopausal women (mean ? SD: age 65.2 ? 4.6 years, body mass index 33.7 ? 4.9 kg/m(2)) were prescribed a reduced calorie diet (1,400 kcal/day; 15%, 65%, 30% energy from protein, carbohydrate, and fat, respectively) and randomly assigned to 2 ? 25 g/day whey protein (PRO n = 15) or maltodextrin (CARB n = 16) supplementation for 6 months. Lean soft tissue (LST) via dual-energy X-ray absorptiometry; thigh muscle, subcutaneous adipose tissue (SAT), and intermuscular adipose tissue with magnetic resonance imaging; knee strength with isokinetic dynamometry; balance and physical function with a battery of performance tests.
RESULTS:
PRO lost more weight than CARB (-8.0% ? 6.2%, -4.1% ? 3.6%, p = .059; respectively). Changes in LST, %LST, and strength, balance, or physical performance measures did not differ between groups (all p > .05). Weight to leg LST ratio improved more in PRO versus CARB (-4.6 ? 3.6%, -1.8 ? 2.6%, p = .03). PRO lost 4.2% more muscle (p = .01), 10.9% more SAT (p = .02), and 8.2% more intermuscular adipose tissue (p = .03) than CARB. Relative to thigh volume changes, PRO gained 5.8% more muscle (p = .049) and lost 3.8% greater SAT (p = .06) than CARB. Weight to leg LST ratio (r(2) = .189, p = .02) and SAT (r(2) = .163, p = .04) predicted improved up and go, relative muscle (r(2) = .238, p = .01) and SAT (r(2) = .165, p = .04) predicted improved transfer test, and %LST predicted improved balance (r(2) = .179, p = .04).
CONCLUSIONS:
A higher protein intake during caloric restriction maintains muscle relative to weight lost, which in turn enhances physical function in older women.

Source: J Gerontol A Biol Sci Med Sci. 2011 Jul 27.

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